This invention relates generally to a method and apparatus for directional blasting for use in the mining and construction industries and like operations.
In the present state of the art of blasting, a drill hole is filled with explosives which are ignited resulting in the blow-out coming to where there is the least resistance, in other words to the nearest face of the rock. The difficulty is that the explosion also shatters or weakens the rock structure above or beyond the drill hole and in the opposite direction from which it is desired the explosion should take place. This necessitates a considerable amount of timbering up of ceilings, walls etc., to provide support to those areas damaged by the explosion. The idea of the present invention is to direct the blasting effect in a desired direction thereby causing as little damage as possible to the adjacent rock areas.
Some techniques of directional blasting are known in the art. However in the present state of the art, blasting tubes are inserted into bore holes, and the blasting tubes are required to be filled with stemming material (such as water or sand etc.) when the tube is placed in position in the bore hole prior to detonation. In the prior art, metallic or thermoplastic materials are used in construction of the blasting tubes. The principle they work on is that the stemming material receives a portion of the explosive force while the material to be blasted receives the other portion of the explosive force, thereby directing the blast in the direction opposite to which the stemming material is oriented in the bore hole. The prior art is inadequate in that the degree of success was minimal and it requires transportation to the blasting site of stemming material such as water, sand etc., and the need for a time consuming filling operation whereby the blasting tube is filled with the stemming material. Also, at least one end of the blasting tubes, in the prior art, is required to be closed in order to contain the stemming material.